Behaviorism is a philosophy that everything organisms do is called a "behavior" and psychological disorders are treated by modifying the environment and changing behavior patterns. Ivan Pavlov conducted experiments with dogs where he conditioned them to drool when they heard a bell by ringing the bell when presenting food, demonstrating classic conditioning. According to behaviorists, people and animals learn behaviors through systems of rewards and punishment, and people are conditioned over time based on both positive and negative reinforcements they receive.